In recent vehicles, there are vehicles having a steering device of a by-wire (By Wire) system in which driver's steering intension is transmitted to steered wheels through conversion into an electric signal through wires. In the steering device of the by-wire system, a steering direction and a steering quantity by the driver are converted into electric signals which are supplied to a steering device including a steering motor. In response to this, the steering device operates to turn the steered wheels in accordance with the steering intention of the driver by driving the steering motor in accordance with an electric signal (for example, see Patent document 1).
According to the steering device of the by-wire system, for example, during traveling on a road surface having undulations such as a rut, though one of a pair of the steed wheels arranged in a vehicle width direction falls into a part of the road surface having the undulations, this can suppress occurrence of uncontrollable state of the steering wheel by generation of yaw-moment in the vehicle body. As a result, this can reduce an operation load of the steering wheel on the driver.